ZOOM LENS

摘要

PROBLEM TO BE SOLVED: To provide a zoom lens that has a small size and a high variable power ratio suitable primarily for a monitoring video camera, by employing a four-group zoom method in which a variable power group consists of negative and positive lens groups in order from the object side and by properly setting a refractive power of each group. SOLUTION: The zoom lens is equipped with a 1st lens group G1 having positive refractive power, a 2nd lens group G2 having negative refractive power, a 3rd lens group G3 having positive refractive power, and a 4th lens group G4 having negative refractive power. The 2nd and the 3rd lens group move on an optical axis as a variable power group. In addition, the zoom lens is constituted to satisfy the following conditional expressions (1), (2). Where f1, f2 and f3 denote the focal length of the 1st, 2nd and 3rd lens groups G1, G2 and G3 respectively, and where ft denotes the focal length of the whole system in the telephoto end, the conditional expressions are: 0.24